You, know I watched a vid from ModelManTom recently where he reviewed side-firing fiber optics. He gave them a pretty good test and they looked like a nice way of lighting engines like this.

I don't know if you'd try yet another method, but I thought it was interesting.

Also, you're in the UK right? Or am I think of someone else, so I don't know of the availability here.

Here it is:-

Tools: Side Firing Fiber Optics